A. Braathen et al., Application of a critical wedge taper model to the Tertiary transpressional fold-thrust belt on Spitsbergen, Svalbard, GEOL S AM B, 111(10), 1999, pp. 1468-1485
The Tertiary opening of the North Atlantic Ocean involved major and long-li
ved overall dextral transpression between the Svalbard and Greenland plates
. On Spitsbergen, this tectonic event is manifest as a 100-200-km-wide cont
ractional fold-thrust belt in the form of an east-pinching prism. This belt
can be subdivided into (1) a western, basement-involved hinterland provinc
e that reveals more complex deformation, including thrust, transcurrent, an
d normal faulting, and (2) an eastern thin-skinned fold-thrust belt with st
ructures oriented subparallel (north-north west-south-southeast) to the tra
nsform plate boundary.
The time-space distribution and interaction of different structural styles
of Tertiary deformation evident on Spitsbergen support a model with Linked,
long-term and short-term (episodic) dynamic growth of a composite contract
ional and transcurrent fold-thrust wedge. The growth of a narrow, high-tape
r (critical-supercritical) contractional wedge occurred during northward-di
rected crustal shortening (stage 1) in an oblique, dextral transcurrent set
ting. Crustal thickening in the form of thrust uplift and basin inversion a
nd strike-slip duplexing during the main contractional event (stages 2 and
3) created an unstable, supercritical wedge of basement and cover rocks in
the hinterland. At the same time, a broader and more homogeneous frontal pa
rt of the wedge developed eastward by in-sequence imbrication in order to r
educe the taper angle. Local erosion and lateral wedge extrusion (stages 3
and 4) modified the oversteepened hinterland wedge to a critical taper angl
e. Continued tectonic activity in the hinterland caused renewed internal im
brication of the frontal wedge, where deformation was accommodated by tear
faulting and out-of-sequence thrusting (stage 4). Adjustment toward a stabl
e taper geometry included local extension (stage 5) and erosion and sedimen
tation.
In a transpressional fold-thrust belt, as on Spitsbergen, out-of-plane (oro
gen oblique to parallel) transport in the hinterland may cause local and la
teral supercritical and subcritical wedge tapers. Hinterland geometries cou
ld trigger adjustments in a frontal thrust wedge in a decoupled situation,
and/or orogen oblique or parallel motions in a coupled situation. Changing
kinematics may thus be expected along strike in such an orogen.